In the field of photomechanical process technology, photographic materials with excellent original-producibility, stable processing solutions and a simplified replenishment system are required for dealing with diversified and complicated print forms currently in use.
Originals employed in a line work process often are composed of phototypeset letters, hand-written letters, illustrations and halftone dot image photographs. Accordingly, the original contains plural images differing concentration and differing line width in combination. Photomechanical cameras and photographic materials capable of finishing the images from such originals with good reproducibility, as well as image-forming methods applicable to such photographic materials are desired earnestly. On the other hand, for the photomechanical process of producing catalogs or large-sized posters, blow-up or reduction of dot image photographs is effected widely. In the photomechanical process of using enlarged dot images, the dots are coarsened to give blurred photoprints. As opposed to this, in the photomechanical process for forming reduced photoprints, fine dots with an enlarged ratio of lines/inch are photographed. Accordingly, an image-forming method with much broader latitude is desired for the purpose of maintaining the reproducibility of halftone dot images in the photomechanical process.
As the light source for a photomechanical camera, a halogen lamp or xenon lamp is employed. To obtain sufficient photographing sensitivity to the light source, the photographic material employed in the photomechanical process is generally ortho-sensitized. However, it was found that ortho-sensitized photographic materials are influenced greatly by the chromatic aberration of a lens and therefore the quality of the images frequently is worsened by such an influence. It was further found that the deterioration of image quality is more noticeable when a xenon lamp is used as the light source.
As a system of attempting to satisfy the demand for broad latitude, a method is known where a lith-type silver halide photographic material composed of silver chlorobromide (having a silver chloride content of at least 50% or more) is processed with a hydroquinone-containing developer where the effective concentration of the sulfite ion therein is lowered extremely (generally, to 0.1 mol/liter or less) to obtain thereby a line image or halftone dot image having a high contrast and a high blackened density where the image portions and the non-image portions are clearly differentiated from each other. However, the method has various drawbacks. Precisely, since the sulfite concentration in the developer is low, development is extremely unstable to air oxidation. For the purpose of stabilizing the activity of the processing solution, various means are effected. The processing speed is extremely slow and the working efficiency is poor.
Accordingly, an improved image-forming system is desired which is free from the instability of the image formation in the above-mentioned development method (lith-development system) and which may be processed with a processing solution having an excellent storage stability to give photographic images having ultra-hard photographic characteristics. As one example, a system of forming an ultra-hard negative image having a gamma value of more than 10 has been proposed, for example, in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781, where a surface latent image-type silver halide photographic material containing a particular acryl hydrazine compound is processed with a developer which has an excellent storage stability and which contains a sulfite preservative in an amount of 0.15 mol/liter or more, under the condition of a pH value of from 11.0 to 12.3. The proposed image-forming system has the characteristic aspect that a silver iodobromide or silver chloroiodobromide-containing photographic material can be processed, although only a high silver chloride content-having silver chlorobromide photographic material can be processed by the conventional ultra-hard image-forming method.
The proposed image-forming system is excellent in that an image with a sharp halftone dot image quality is formed, the process proceeds stably at a high speed and the reproducibility of the original used is good. However, a further improved system with a further elevated original reproducibility is desired still for the purpose of satisfactorily dealing with the diversified print forms currently in use.
JP-A-61-213847 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and U.S. Pat. No. 4,684,604 disclose photographic materials containing a redox compound capable of releasing a development inhibitor by oxidation in an attempt at broadening the latitude of reproduction of gradation of images. However, where such a redox compound is added to a photographic material to be processed in an ultra-hard processing system using a hydrazine derivative in an amount sufficient for satisfactorily improving the reproducibility of reproducing both line images and halftone images, a part of the development inhibitor released from the redox compound would flow into the processing solution for development. As a result, when a large amount of such a photographic material containing a redox compound of the kind is processed continuously, the released development inhibitor would accumulate in the developer tank. When development is continued with such a fatigued developer, the formation of hard images is impossible and the sensitivity of the photographic materials being processed is decreased. In particular, where one automatic developing machine is used for processing photographic materials containing such a redox compound and also for processing other various picture-taking photographic materials, contact-printing photographic materials, scanning photographic materials and photocomposing photographic materials, there occurs a problem that the development inhibitor as released from the redox compound often has a bad influence on the photographic properties of other photographic materials.
Because of these reasons, the amount of the redox compound used is limited so that the effect of the redox compound is not displayed sufficiently, or the photographic material having such a redox compound must be processed with specifically defined processing solutions and only in a specifically closed system. Such limitation or use of such a closed system is inconvenient.